Welcome to PICU Doc On Call, A Podcast Dedicated to Current and Aspiring Intensivists.
I'm Pradip Kamatand I'm Rahul Damania. We are coming to you from Children's Healthcare of Atlanta - Emory University School of Medicine.
Welcome to our Episode of a 19 month old female with bloody stool, petechiae and no urine output
Here's the case presented by Rahul:
A 19 month old previously healthy female was brought to the pediatric emergency department for blood in her stool. Patient was at daycare the previous day where she developed a low grade fever, congestion and URI symptoms along with non-bloody-non-bilious vomiting and diarrhea. Patient had a rapid COVID test which was negative and was sent home with instructions for oral hydration. That evening, patient began having vomiting/diarrhea which worsened. She was unable to retain anything by mouth and her parents also noted blood in her stool.
Due to this, she was rushed to the Emergency Department. In the ED here, she was hypertensive for age BP of 124/103 mm Hg, febrile, and ill. Specks of blood were noted on the diarrheal stool in the diaper.
On her physical exam she was noted to be pale with petechiae on neck and chest. Her abdomen was soft, ND, with some hyperactive bowel sounds, and no hepatosplenomegaly. The rest of her physical examination was normal.
In the ED, initial labs were significant for WBC 19, Hgb 8.8, and Platelets 34. CMP was significant for BUN of 74mg/dL and Cr of 3.5mg/dL, Na 131 mmol/L, and K of 5.5mmol/L, Ca 8.3mg/dL (corrected for albumin of 2.2g/dL), Phosphorous 8.5 AST 413, and ALT of 227, LDH > 4000. BNP was 142 and troponin negative. She was given 1 dose of CTX 50mg/kg and a 20cc/kg NS bolus. Stool PCR was sent. She was given labetalol for her hypertension, started on maintenance IV fluids and transferred to the PICU for further management.
Rahul to summarize key elements from this case, this patient has:
All of which bring up a concern for hemolytic uremic syndrome the topic of our discussion today
Let's transition into some history and physical exam components of this case.
What are the key historical features in this child who presents with above?
Are there some red-flag symptoms or physical exam components which you could highlight?
To continue with our case, the patient's labs were consistent with:
OK to summarize, we have a 19 month old girl with:
Rahul Let's start with a short multiple choice question:
A 2-year old boy is admitted to the PICU with acute respiratory failure secondary to pneumococcal pneumonia. On day # 3 of admission, the nurse reports the patient appears pale and has petechiae on his chest. The patient also has not had urine output for > 12 hours and appears to be fluid overloaded. Of the following the lab findings would be most consistent with the above clinical findings in the patient?
Patient in the above case most likely has streptococcus pneumoniae associated hemolytic uremic syndrome commonly called as pneumococcal HUS, an uncommon condition, which accounts for 5% of all cases of HUS in children. A peripheral smear will show the presence of schistocytes (which consists of fragmented, deformed, irregular red blood cells). The schistocytes represent RBCs that are partially destroyed as they traverse through the blood vessels partially occluded by microthrombi. Smear may also show giant platelets due to the rapid platelet turnover from peripheral destruction. Because HUS is an intravascular hemolysis serum haptoglobin should be low. Serum LDH along with indirect bilirubin are typically elevated. The Direct Coombs test detects antibodies that coat RBCs and may allude to this pathology. In pneumococcal HUS where there is antigen-antibody interaction on RBC cell surface, the Direct Coombs test may be positive in 90% of the cases. A direct Coombs test is highly sensitive for pneumococcal HUS, but the degree of specificity is unclear.
A few points which I want to highlight classically on board exams, schistocytes look like helmet cells on blood smear. Also, presence of COOMBs positivity in the setting of hemolysis think about autoimmune hemolytic anemia (AIHA).
The following may sometimes be difficult to differentiate from HUS
Rahul, before we go into the diagnostic and management framework can you shed some light on the pathogenesis of HUS?
The hemolytic uremic syndrome comes under an umbrella term called Thrombotic microangiopathy (TMA) syndromes. The clinical features of TMA include microangiopathic hemolytic anemia, thrombocytopenia, and organ injury. The pathological features are vascular damage that is manifested by arteriolar and capillary thrombosis with characteristic abnormalities in the endothelium and vessel wall.
Let’s breakdown the three pathogenesis or sub-diagnoses:
Pradip, what is the second subtype?
Finally, let’s talk about atypical HUS.
Atypical HUS or complement mediated HUS accounts for approximately 10% of cases seen in children - what is the pathophysiology of this disease?